In general, in a piston type compressor such as a swash plate type compressor, cylinder blocks and a set of a suction chamber and a discharge chamber are defined while intervening a valve plate therebetween. In the valve plate, suction ports are formed in positions leading to the suction chamber and discharge ports are formed in positions leading to the discharge chamber. Then, a suction valve is disposed on a surface of the valve plate on the cylinder block side and a discharge valve is disposed on the other surface thereof on the side of the suction chamber and discharge chamber. The suction valve has suction reed portions at positions corresponding to the suction ports, and the discharge valve has discharge reed portions at positions corresponding to the discharge ports.
During the operation of such a compressor, the suction reed portions of the suction valve and the discharge reed portions of the discharge valve are adapted to open and close the suction ports and the discharge ports of the valve plate in accordance with the reciprocating motion of pistons. However, these reed portions are brought into tight contact with the surface of the valve plate due to the surface tension since lubricant component contained in a refrigerant adheres thereto. Accordingly, it is known that an instantaneous pressure variation is generated during the opening/closing operation of the suction ports and the discharge ports, thus inducing generation of an abnormal sound from an evaporator connected to the compressor, or exacerbating the noise and vibration caused accompanying collision of the reed portions.
Accordingly, in Japanese Patent Non-Examined Publication (Kokai) No. 2-218875 filed by the present applicant, it is proposed to realize quietness of the operation by roughening the surface of the valve plate with which the suction valve and the discharge valve are to be brought into contact.
It is possible to suppress the generation of the noise and vibration in the opening/closing operation of the suction valve and the discharge valve by such roughening of the surface of a valve plate. Conventionally, a shot blast method of blasting shot grains made by alumina and so on with air pressure has been used to roughen the surface. After the shot grains are blasted onto the surface of the valve plate which are masked in a predetermined pattern, the surface of the valve plate is cleaned.
However, there is a risk that, even if it is cleaned, process scraps produced during the roughening operation or the shot grains per se would remain as foreign matter on the surface of the valve plate. If such foreign matter intrudes into the compressor, operation failure or breakdown of the compressor would be caused as a result.